A tree processing machine, such as, for example, a forestry harvester, may be used to fell and/or process trees. For example, a tree processing machine may include a tree processing unit (e.g., a tree processing head) used to cut off a tree trunk near its base, remove at least a portion of the bark and/or limbs from the tree, and/or cut the tree's trunk into a number of sections based, for example, on length. Some forestry harvesters may include, for example, a robust all-terrain vehicle that may be driven via wheels and/or tracks. For example, some forestry harvesters may include an articulated chassis to provide tight turning capability for maneuvering around obstacles. Some forestry harvesters may include a compression-ignition engine providing power for propelling the harvester as well as a tree processing head, for example, via a hydraulic drive mechanism. The tree processing unit may be coupled to the forestry harvester via a boom, such as an extensible, articulated boom, which facilitates movement of the tree processing unit for engaging the tree, cutting the tree off near the ground, and processing the tree. For example, some forestry harvesters are adaptations of existing excavators, which have been modified by replacing a bucket with a tree processing unit, and other forestry harvesters are purpose-built machines.
A typical processing unit may include, for example, a feed roller configured to feed a portion of a tree trunk through the processing unit. The feed roller may include a wheel configured to grip and rotate as the tree trunk is fed through the processing unit, and the feed roller may be operably associated with a sensor configured to generate signals indicative of the length of travel of the tree trunk through the processing unit. For example, the feed roller may be associated with a rotary encoder that may include an electro-mechanical device configured to convert angular displacement of the feed roller into an analog or digital signal to facilitate determination of the length of tree trunk passing through the processing unit.
Such encoders are conventionally mounted on a shaft associated with the feed roller in a manner such that they are exposed to the environment and/or vibrations associated with operation of the forestry harvester. Because encoders may include electronic devices, however, they may be sensitive to vibrations associated with the environment and/or operation of the forestry harvester. This may interfere with reliable operation of the encoder and/or prematurely result in damage to the encoder.
For example, U.S. Pat. Pub. No. 2008/0128051 to Isley et al., published on Jun. 5, 2008 (“the '051 application”), discloses a system for measuring the length of a tree being processed through a delimber. The delimber in the '051 application includes a log feed roller for moving the tree, a delimbing head for delimbing the tree, and a measuring wheel mounted on the delimbing head. Although the measuring wheel disclosed in the '051 application may provide measurements of the length of the tree being processed, because the measuring wheel is mounted on the delimbing head, it may be exposed to the harsh conditions during the operation of the delimber, and the measurement provided by the measuring wheel may be subjected to influence by machine vibrations.
The apparatuses of the present disclosure may be directed toward improvements in the existing technology.